William Samuel was the only bapt where the mother's surname was given, so good pickup Donna!
But it does raise a question about whether the clerk was sure of her surname, and if not, why not.
I have found a couple of instances where people apparently didn't bother to marry because their names/surnames were already the same. There are these two bapts in Maughold, but probably too late to be the right Jane:
Ann Jane dau of Edward Christian & Isab Kermeen 27 Jun 1831.
Jane Christian dau of Thomas Kneale & Ann Kennish 16 Oct 1831.
William Kinrade & Ann Creech were having children baptised in Maughold around the time that she would have been born, but no sign of Jane.
I thought this was a possibility:
Jane dau of Pat Corkill & Cath Creech bapt 27 Dec 1826. Was she looked after as a baby by Ann (Creech) Kinrade because Patrick Corkill was ill? He was "incapable" in 1836, and Ann and Cath Creech were first cousins. Ann had a daughter born the same year as Jane who died after a few months, as had her previous child.
The problem with this theory is that Jane was listed with the Corkills in 1841.